What is Encephalitis, types, treatment, prevention, has a cure?

What is encephalitis?

Encephalitis is an acute inflammation of the brain, usually caused by viral or bacterial infections. If left untreated, it can have serious consequences.

Have you noticed that infection in the brain is rarely spoken of, even though infections in many other parts of the body are normal? Well, this is because the brain is extra-protected by the immune system, which makes infections in this organ quite rare.

This does not mean, however, that everyone is safe: babies, children and people with weakened or compromised immune systems are great candidates, and these are also the groups that suffer the most sequelae.

Inflammation can be triggered either by direct infection of a microorganism in the brain or as a response to infections elsewhere in the body. In addition, there are cases of autoimmune background encephalitis.

Although encephalitis can easily be resolved by the self-limited nature of viral infections, it can also cause severe sequelae in patients who do not follow treatment correctly.

Causes of encephalitis

In general, encephalitis is caused by infectious agents such as viruses, bacteria, parasites and fungi, which can be transmitted in many different ways.

The infection can be primary or secondary. In the primary, the microorganism infects the brain directly, while in the secondary, the problem is in the immune system that is mistaken and, instead of attacking the cells that cause the infection, it attacks healthy brain tissue.

There are several viruses, microorganisms and conditions that can cause encephalitis. Some examples are:

Herpes simplex

The main causative agent of encephalitis is the herpes simplex virus, the same that causes those flat blisters that itch on the lips. Occasionally, the virus manages to cross the resistance and reach the central nervous system, generating a local inflammatory response.

It is worth remembering that both herpes simplex 1 (related to the blisters in the corner of the mouth) and 2 (which causes genital herpes ) are capable of causing and encephalitis. However, infection by type 1 is more rare than type 2.

Other herpes viruses

Herpes is not just one virus, but several. Other viruses of this type that can cause encephalitis are Epstein-Barr (mononucleosis) and varicella zoster ( chicken pox and shingles).


Viruses belonging to the enterovirus genus, such as Coxsackievirus, may also be responsible for encephalitis. Symptoms of infections of these types of viruses include symptoms similar to flu , eye inflammation and abdominal pain.

Viruses transmitted by mosquitoes

Some viruses that are transmitted by mosquitoes have encephalitis as a complication. Some examples are dengue , malaria , chikungunya , yellow fever , among others.

There are also tick-borne viruses that can reach the brain.


Causing rabies , the Lyssavirus affects the host’s central nervous system. Infection with this virus evolves rapidly, increasing the chance of brain damage from swelling of the brain.

Childhood infections

Several viruses of classic childhood diseases, such as measles , rubella and mumps , can also cause encephalitis – usually of the secondary type.


Vaccines can also be the cause of encephalitis, due to the possible reactivation of these microorganisms in the patient. In addition, there is also the possibility of direct infection by bacteria and fungi, which usually give rise to abscesses.

Other causes

Autoimmune diseases and cancer side effects are also on the list of culprits for inflammation in the brain, even though it is not always clear why the inflammation is triggered.

Risk factors

Although anyone is subject to the development of encephalitis, the main risk factors for the disease are:


There are some viruses that are more frequent during childhood, while others affect older people. This can occur because of a weakened immune system or because of immunizations.

Immune system problems

People with a weakened immune system for some reason are more susceptible to any type of infection, in addition to making it easier for microorganisms to reach the brain. HIV patients who take drugs that weaken the immune system or have any other condition that affects their functioning are great candidates for the development of the disease.

Geographic regions and times of the year

When it comes to viruses transmitted by mosquitoes and ticks, some regions and seasons can be a risk factor for infection. This is because these animals have a predilection for hot climates and are more active during the summer.

Children receiving vaccines

Triple viral, measles, rubella and mumps vaccine , is a risk factor for encephalitis. That’s because 1 in 3,000 vaccinated children develop the disease. However, this is no reason to stop taking the vaccine: before it was available, that proportion was 1 in 1,000 children.

Encephalitis and meningitis: is there a difference?

Although these two diseases affect the brain, there is a big difference between encephalitis and meningitis , especially in relation to the affected area.

Meninges are protective membranes that surround the brain and are the main ones affected by meningitis. Infections in these membranes are usually caused by bacteria rather than viruses.

In the case of encephalitis, the infection is mainly caused by viruses, and the affected area is the brain itself, not just its lining. In addition, the symptoms of the latter are more severe and include disturbances of consciousness and motor signs.

Is encephalitis transmissible?

Because it is caused by several viruses and microorganisms, encephalitis is transmissible . What varies, in this case, is the way of transmission.

Some of the viruses that cause the problem are transmitted through saliva and respiratory droplets, others can be through contaminated food and drinks, while there are still some that are transmitted in direct contact with the skin.

Depending on the geographic region, encephalitis can be the result of zoonosis, that is, viruses, bacteria or protozoa can be transmitted through insect and tick bites.


Although many believe that there is only one type of encephalitis – viral – it can be classified in different ways according to its origin and duration. Understand:

Infectious encephalitis

This is the type of encephalitis caused by infectious diseases, such as measles and polio . It may be the result of a direct infection or as a response of the body to an infection elsewhere.

When caused by the herpes simplex virus, it is also known as herpetic encephalitis and can be fatal.

Postinfectious encephalitis

Usually a result of reactivating a virus, post-infectious encephalitis can occur weeks or months after the infection has resolved.

Autoimmune encephalitis

In some cases, the immune system starts to attack the myelin sheath – a tissue that surrounds and protects nerve cells.

This usually happens after infections or vaccines whose microorganisms have proteins very similar to those found in this lining of the nerves. Thus, the immune system gets confused and starts to attack healthy tissues, believing that there is an infection.

The main viruses that trigger this reaction are enteroviruses, Epstein-Barr virus, HIV and hepatitis A and B viruses.

Chronic encephalitis

In some cases, inflammation occurs slowly and gradually, as in the case of HIV infections. It can also be caused by Rasmussen Syndrome, a neurological disorder characterized by frequent and severe epileptic attacks.

Symptoms: how to identify encephalitis?

The symptoms of encephalitis can vary widely, depending on the cause and the part of the brain affected. In general, patients with encephalitis may have:

  • Fever;
  • Headache;
  • Sensitivity to light (photosensitivity);
  • Weakness;
  • Vomiting;
  • Seizure.

Despite these very broad symptoms, depending on the affected areas, some more specific symptoms are:

  • Hallucinations;
  • Poor motor coordination;
  • Slowness in movements;
  • Stiffness in the neck and limbs;
  • Mental confusion;
  • Somnolence;
  • Lethargy – which can progress to stupor and coma;
  • Visual, auditory and sensory changes;
  • Problems in formulating and understanding language;
  • Hormonal changes such as diabetes insipidus, inadequate secretion of antidiuretic hormone, among others.

In babies

Unfortunately, babies are unable to express what they are feeling, so parents should be aware of the signs it shows. Some examples are:

  • Bump on the soft spot (fontanelle), which indicates brain swelling;
  • Nausea and vomiting;
  • Body stiffness;
  • Do not breastfeed properly or do not wake up to breastfeed;
  • Irritability.

If you notice any of these signs in your child, take them to the doctor immediately , as young children may not be able to resist the disease.

How is encephalitis diagnosed?

Based on the reported symptoms, the doctor – who may be a general practitioner, emergency doctor, infectious disease or neurologist – may suspect encephalitis and order a battery of tests to confirm the diagnosis. Some of these tests are:

Lumbar puncture

The lumbar puncture exam consists of collecting a fluid that travels and irrigates the entire nervous system, called cerebrospinal fluid – or cerebrospinal fluid. It can be found both in the brain and surrounding the spinal cord.

In the same way that microorganisms circulate in the blood in the most common infections, the causes of encephalitis also circulate in this cerebrospinal fluid. Thus, in addition to being able to detect the presence of some microorganism, in some cases it can be identified as well.

Magnetic Resonance Imaging (MRI)

In order to check which part of the brain has been affected, the doctor may order an MRI scan. This test uses a magnetic field to generate images of the brain in the form of “slices”, which facilitates the visualization of anomalies.

If it is not possible to perform an MRI scan, you can alternatively order a CT scan, an exam that generates the same type of image, but with the use of X-rays.

Some infectious agents have a kind of “preference” for certain areas of the brain, so the findings from these tests may help to detect which microorganism is responsible for encephalitis.

Electroencephalogram (EEG)

The electroencephalogram is an exam that monitors the electrical activity of the brain. With it, it is possible to identify changes in the electrical function of the affected areas, which may suggest a specific microorganism. In the case of herpes simplex, for example, there are changes in activity in the temporal lobes – the portion of the brain near the ears.

Polymerase chain reaction (PCR)

The PCR is a technique that produces multiple copies of a gene, facilitating the work to detect the genetic material of the virus and its subsequent identification. Some types of virus are more dangerous than others, such as herpes simplex, which, when left untreated, can have serious consequences.


Rarely, when previous tests have not given satisfactory results, a biopsy may be requested, which is the removal of a sample of brain tissue. This sample is sent for analysis, where it is easier to detect the infectious agent responsible for the disease.

When no microorganism is found, even after all these tests, encephalitis is believed to be the product of cancer or autoimmune origin, types that are not easily detected by laboratory tests.

Is encephalitis curable?

In most cases, encephalitis is curable , as the life cycle of viruses within an organism is self-limiting. In spite of this, one should not fail to seek treatment because the lack of symptom relief can cause serious sequelae, mainly due to the brain swelling that can damage it.

In other cases, such as autoimmune and chronic encephalitis, the prospect of a cure is somewhat distant.

How to treat encephalitis?

As with most viral infections, the treatment of encephalitis is based on symptom relief, as leaving them untreated can be harmful to the body.

In some cases, such as infections with herpes simplex, herpes zoster and cytomegalovirus, there are antiviral drugs that help in the treatment. In the case of HIV, anti-retroviral drugs help the immune system to function and slow down the progression of the infection.

When there is a bacterial infection, antibiotics can be administered .

Corticosteroids (anti-inflammatory drugs) are used to relieve swelling of the brain, which can harm the organ due to pressure against the skull bones. In the case of seizures , administration of anticonvulsants is often recommended.

In the simplest cases, the remission of the infection occurs between 1 and 2 weeks.

It is worth remembering that, often, treatment must be done in a hospital environment, since brain involvement requires close monitoring.

Encephalitis medications


  • Aciclovir;
  • Ganciclovir.


  • Betametasona;
  • Dexamethasone .


  • Carbamazepine ;
  • Phenytoin .


  • Paracetamol to reduce fever and headache.


NEVER self-medicate or stop using a medication without first consulting a doctor. Only he will be able to tell which medication, dosage and duration of treatment is the most suitable for his specific case. The information contained in this website is only intended to inform, not in any way intended to replace the guidance of a specialist or serve as a recommendation for any type of treatment. Always follow the instructions on the package insert and, if symptoms persist, seek medical or pharmaceutical advice.

Sequelae of encephalitis

When it is not treated properly or does not respond to treatment, encephalitis can cause serious sequelae. That’s because the brain suffers swelling and is under pressure from the cranial box, which can lead to injuries in certain parts.

Some of these sequels are:

  • Muscular paralysis;
  • Memory and learning problems;
  • Difficulties in speech and hearing;
  • Visual and sensory changes;
  • Epilepsy;
  • Involuntary muscle movements.

Encephalitis kills?

Although, in most cases, it is a disease of short duration and easy resolution, encephalitis can kill , especially in the case of children, the elderly and immunocompromised people, who have difficulty in fighting the infectious agent.

This is because the pressure of brain inflammation tightens the brain stem, part of the brain responsible for vital functions such as breathing, heartbeat, among others. When this structure is damaged, these functions stop, causing death.

Herpes simplex brain infection can lead to death quickly if it is not promptly diagnosed and treated.


The prognosis of encephalitis depends on several factors such as the causative microorganism, age and condition of the immune system.

Patients who were healthy before infection tend not to have many problems after infection. Patients with compromised immune systems, such as those with AIDS , cancer or who use immunosuppressants, usually have a lot of sequelae.

When talking about untreated herpes simplex encephalitis, the mortality rate is 50-75%. In addition, when treatment is delayed, practically all patients develop sequelae.

However, when there is treatment, mortality drops to 20%, with sequelae equal to those present at the time of the first dose of antiviral. It is estimated that 40% of the survivors have mild and moderate sequelae such as problems with learning, memory, epilepsy , neuropsychiatric abnormalities, among others.

It is worth remembering that people who go into a coma due to encephalitis will not necessarily have more sequelae than those who have not lost consciousness. There are many reports of patients who woke up from a coma with little or no sequela.

Infections with viruses transmitted by insects and ticks are much worse, with sequelae similar to those of infection with herpes simplex without treatment.

How to prevent encephalitis?

The prevention of encephalitis can be done in several ways, since there are many microorganisms capable of causing brain inflammation. Some tips for this are:

  • Wash your hands with soap and water frequently;
  • Do not share glasses, plates, cutlery and personal effects;
  • Always take your children to the doctor when they present symptoms of common childhood diseases such as measles, mumps, among others;
  • Do not miss the child vaccination campaigns against measles, mumps, rubella, chicken pox, flu, polio, among others;
  • People traveling to other countries must be properly vaccinated against endemic infections, such as Japanese and tick-borne encephalitis;
  • Vaccines against the H. influenzae B virus, meningococcus and pneumococcus can help prevent encephalitis as a complication of these infections.

Although rare, encephalitis is not a very easily identifiable disease that needs to be treated as quickly as possible due to the possibility of serious sequelae.

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